/ 
Geo-Horizon-0.01
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/ Geo::Horizon

NAME

Geo::Horizon - Calculate distance to the visual horizon

SYNOPSIS

use Geo::Horizon;
my $gh = Geo::Horizon->new("WGS84");
my $lat=39;
my $alt=1.7;
my $distance_to_horizon=$gh->distance($alt,$lat);
print "Input Lat: $lat1\n";
print "Output Distance: $dist\n";

DESCRIPTION

A perl object of calculating the distance to the visual horizon on an ellipsoid.

CONSTRUCTOR

new

my $gh = Geo::Horizon->new(); #default WGS84

METHODS

ellipsoid

Method to set or retrieve the current ellipsoid object. The ellipsoid is a Geo::Ellipsoids object.

my $ellipsoid=$gh->ellipsoid;  #Default is WGS84

$gh->ellipsoid('Clarke 1866'); #Built in ellipsoids from Geo::Ellipsoids
$gh->ellipsoid({a=>1});        #Custom Sphere 1 unit radius

distance

The straight-line of sight distance to the horizon:

my $dist=$obj->distance($alt, $lat);
my $dist=$obj->distance($alt);       #default lat => 0

Formula from http://newton.ex.ac.uk/research/qsystems/people/sque/physics/horizon/

Ds = sqrt(h(2R + h))

The curved distance along the ellipsoid to the horizon:

my $dist=$obj->distance_great_circle($alt, $lat);
my $dist=$obj->distance_great_circle($alt);
my $dist=$obj->distance_great_circle();

Formula from http://newton.ex.ac.uk/research/qsystems/people/sque/physics/horizon/

Dc = R acos(R / (R + h))

TODO

BUGS

Please send to the geo-perl email list.

LIMITS

AUTHOR

Michael R. Davis qw/perl michaelrdavis com/

LICENSE

Copyright (c) 2006 Michael R. Davis (mrdvt92)

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

SEE ALSO

Geo::Ellipsoids